Modern electronics, such as smart phones, personal digital assistants, location based services devices, servers, and storage arrays, are packing more integrated circuits into an ever shrinking physical space with expectations for decreasing cost. Numerous technologies have been developed to meet these requirements. Some of the research and development strategies focus on new package technologies while others focus on improving the existing package technologies. Research and development in the existing package technologies may take a myriad of different directions.
In the electronics industry, a continuing goal has been to reduce the size of electronic devices, such as camcorders and portable telephones, while increasing performance and speed. Integrated circuit packages for complex electronic systems typically have a large number of interconnected integrated circuit chips. The integrated circuit chips are usually made from a semiconductor material such as silicon or gallium arsenide. After manufacture, the chips are typically incorporated into packages that are then mounted on printed circuit wiring boards.
Integrated circuit chip packages typically have numerous external pins that are mechanically attached by solder or a variety of other known techniques to conductor patterns on the printed circuit wiring boards.
Typically, the packages in which these integrated circuit semiconductor chips are mounted include a substrate or other chip mounting device. One example of such a substrate is a lead frame. More particularly, a lead frame is a metal frame that includes a centrally located die paddle or die pad and a plurality of peripherally-located leads that surround the die pad. The die pad mounts the semiconductor chip (or “die”). Power, ground, and/or signal leads of the lead frame are connected electrically by wire bonds to power, ground, and/or signal sites on the chip and serve as external connecting means for the chip.
After the chip is wire-bonded to the leads, the chip, the die pad, and portions of the leads are encapsulated in a plastic, an epoxy-molded compound, or a multi-part housing made of plastic, ceramic, or metal, to form the semiconductor package. The package protects the lead frame and the chip from physical, electrical, moisture, and/or chemical damage.
Some lead frame configurations, for example exposed die pad packages, include a separate ground ring structure that is supported around the periphery of the die pad and inside the inner ends of the leads. The ground ring facilitates the many bonding wire electrical connections that typically must be made to connect ground pads on the die to electrical ground connections on the lead frame.
However, lead frames designed with such a ground ring require additional clearance space (i.e., distance) between the die pad and the ground ring and between the ground ring and the inner tips of the peripherally-located leads. This clearance space is necessary for ease of manufacturing and for proper looping of the bonding wires from the die to the ground ring and from the ground ring to the lead tips. Unfortunately, this increases the lengths of the other bonding wires that connect the die to other (e.g., power and signal) leads on the lead frame.
The requirement for ground ring clearance space thus increases the net distance between the die and the lead tips. Typically, there are more wires that connect dies to the power and signal lead tips than to the ground ring and to the ground lead tips. Hence, a ground ring causes the total wire length per die to increase, which correspondingly increases costs. Not only are costs increased, but the additional wire lengths also make the wires prone to sweeping problems during molding. (“Sweeping” of the bonding wires happens during molding of the semiconductor package. Specifically, sweeping happens when the epoxy molding compound pushes the bonding wires out of position as the epoxy molding compound flows past the bonding wires. Sweeping causes bonding wires to short circuit and/or to break.).
Typically, the ground ring is coated with a metal, such as silver, to improve bonding adhesion between the wires and the ground ring. However, silver forms a weak adhesion with the encapsulation material. This may provide problems causing separation between the integrated circuit die from the die pad.
Thus, a need still remains for an integrated circuit package system providing ground ring while maximizing the integrated die size while reducing die attach separation from the die pad. In view of the ever-increasing need to save costs and improve efficiencies, it is more and more critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.